1. Field of the Invention
The invention relates to a process for producing a semiconductor device with a roughened semiconductor surface.
Such a process is described, for example, in East German Patent DD 251 905 A3. That document discloses a process for producing a light-emitting semiconductor device having a III-V compound semiconductor body, in which the surface is roughened. Contact metallizations, which are formed of a gold-beryllium layer and a gold layer, are applied to sub-regions of the III-V compound semiconductor surface, for the purpose of making electrical contact.
A process is further known from German Published, Non-Prosecuted Patent Application DE 43 05 296 A1, corresponding to U.S. Pat. No. 5,429,954, in which the side surfaces of a mesa-etched LED semiconductor chip are roughened through the use of etching in order to improve output light coupling.
The roughening reduces the total reflection of the light radiation produced in the semiconductor device at the surface. As a consequence thereof, the radiated intensity, and therefore also the external quantum efficiency of the light-emitting semiconductor device, is increased.
However, the contact metallizations made of gold-beryllium and gold cause great difficulties in the production of those semiconductor devices.
Firstly, there are difficulties in automatic optical detection of the gold metallizations. The reason therefor is an unfavorable contrast between the semiconductor surface and the gold contact surface. The camera systems conventionally used in chip assembly lines must be specially adjusted for that material combination. Without that adjustment, reasonably reliable automatic optical detection is not possible. However, any re-adjustment in chip assembly lines entails additional costs.
Great difficulties are also caused by the fact that the junction between the conventionally used gold bonding wire and a gold bonding pad only has low mechanical strength. That increases the risk of the connection wiring being torn off during the chip production, for example during encasing.